The WTC3243 from Wavelength Electronics is a 2.2-A temperature controller designed into electro-optical systems, airborne instrumentation, spectroscopic monitors and medical diagnostic equipment to provide stability, even across ambient. It achieves on-ambient stability of 0.0014 °C with thermistors. The linear proportional integral control loop provides maximum stability, and the bipolar current source is designed for high efficiency. The system maintains precision temperature regulation via an adjustable sensor bias current and error amplifier circuit. The proportional gain and integrator time constant are set by external resistors and can be modified to optimize temperature overshoot and stability.